1. Field of the Invention
The present invention relates to an operation control technique of an electronic apparatus system which can operate using, e.g., a direct methanol fuel cell as a power supply.
2. Description of the Related Art
In recent years, various portable electronic apparatuses such as a portable information terminal called a PDA (Personal Digital Assistant), digital camera, and the like, which can be driven by a battery, have been developed and are prevalent.
Also, recently, environmental problems are widely recognized, and the development of environment-friendly batteries has been extensively made. As a battery of this type, a direct methanol fuel cell (to be abbreviated as DMFC hereinafter) is well known.
This DMFC produces electrical energy by the chemical reaction of methanol as fuel and oxygen. The DMFC has a structure in which two electrodes made up of a porous metal or carbon sandwich an electrolyte (e.g., Hironosuke Ikeda, “All About Fuel Cells”, NIPPON JITSUGYO PUBLISHING, CO., LTD., Aug. 20, 2001, pp. 216-217). Since this DMFC does not produce any hazardous waste, its practical application is strongly demanded.
The DMFC uses an auxiliary mechanism such as a pump or the like to increase the output electric power per unit volume. Therefore, the output electric power of the DMFC can be controlled by controlling the operation ratio of this auxiliary mechanism.
However, in this case, when, for example, the load electric power is measured, and the output electric power of the DMFC is controlled based on the measurement result, a long delay is produced. That is, the electronic apparatus system which operates using the DMFC as a power supply requires a mechanism for attaining a smooth output change of the DMFC.